With the advent of indwelling wire sensors has come the danger to the patient of having a cylindrical wire sensor fatigue from the flexure caused by bodily movement and break off inside the body. Under such circumstances a wire sensor can move through tissue relatively quickly and in an unpredictable manner, potentially posing a threat to the delicate internal organs.
Unfortunately, the typical metal used for such a wire sensor is platinum, which is electrochemically active and generally very useful in sensing applications. Platinum, however, is a weak metal that is easily broken with only a little flexure. Moreover, the electrochemical nature of platinum surfaces is only imperfectly understood. Efforts to make sensors from very thin platinum wires that are stranded together, thereby providing greater flex resistance, have encountered negative effects on the biochemical reactivity of the more complex platinum surface.
Also, platinum is very expensive costing on the order of $25-$30 per gram. For a multiple use sensing assembly incorporating a multiplicity of single use sensing elements, this may be a considerable expense. Also, for sensing elements that double as skin piercing lancets, greater strength is needed than may be available from a small diameter platinum wire. Even for sensors that are to be worn for a few days, the cost of the platinum portion of the sensor can place a strain on the overall budget for a production run of sensors.